Extended leaf phenology and the autumn niche in deciduous forest invasions


The phenology of growth in temperate deciduous forests, including the timing of leaf emergence and senescence, has strong control over ecosystem properties such as productivity1,2 and nutrient cycling3,4, and has an important role in the carbon economy of understory plants5,6,7. Extended leaf phenology, whereby understory species assimilate carbon in early spring before canopy closure or in late autumn after canopy fall, has been identified as a key feature of many forest species invasions5,8,9,10, but it remains unclear whether there are systematic differences in the growth phenology of native and invasive forest species11 or whether invaders are more responsive to warming trends that have lengthened the duration of spring or autumn growth12. Here, in a 3-year monitoring study of 43 native and 30 non-native shrub and liana species common to deciduous forests in the eastern United States, I show that extended autumn leaf phenology is a common attribute of eastern US forest invasions, where non-native species are extending the autumn growing season by an average of 4 weeks compared with natives. In contrast, there was no consistent evidence that non-natives as a group show earlier spring growth phenology, and non-natives were not better able to track interannual variation in spring temperatures. Seasonal leaf production and photosynthetic data suggest that most non-native species capture a significant proportion of their annual carbon assimilate after canopy leaf fall, a behaviour that was virtually absent in natives and consistent across five phylogenetic groups. Pronounced differences in how native and non-native understory species use pre- and post-canopy environments suggest eastern US invaders are driving a seasonal redistribution of forest productivity that may rival climate change in its impact on forest processes.

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Figure 1: Seasonal patterns of leaf emergence and leaf fall for native and non-native species over three growing seasons.
Figure 2: Relative leaf Chl content for native and non-native species.
Figure 3: Proportion of total annual C assimilated in spring and autumn for native and non-native species.


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I acknowledge technical assistance and advice from A. Craddock, S. Anderson, E. Fridley, S. Kelley, A. Surace, L. Giencke and D. Frank, and project support from Syracuse University.

Author information

J.D.F. designed the study, supervised data collection, performed the analyses and wrote the paper.

Correspondence to Jason D. Fridley.

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The author declares no competing financial interests.

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Supplementary Information

This file contains Supplementary Figures 1-3. Figure 1 includes spring heat accumulation over 2008-2010, Figure 2 a comparison of seasonal photosynthetic rate between native and non-native species, and Figure 3 the seasonal light distribution used in carbon gain models. (PDF 428 kb)

Supplementary Table 1

This file contains data and metadata. (XLS 111 kb)

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Fridley, J. Extended leaf phenology and the autumn niche in deciduous forest invasions. Nature 485, 359–362 (2012). https://doi.org/10.1038/nature11056

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